Let's talk about RCD: what it is and how it works

In this age of high technology, people from all sides are surrounded by a huge number of devices and devices that work with electricity. And the more their number, the higher the probability of a person's electric shock. To avoid this, an RCD was invented. What this is and what is needed, we will describe in detail in this article.

Appointment

The device of protective switching-off (RCD) is intended for differential protection of a person from electric shock by touching the body of electrical equipment (household electrical appliances), which in case of insulation failure was energized.

When the RCD trips

Let's continue the story about the RCD. What is it and how does it work? Through the person touching the energized body of the appliance, electrical current begins to flow. When it reaches a value of 30 mA, the RCD trips. As a result, the voltage is automatically disconnected from the damaged equipment. Thus the person feels nothing, as painful sensations arise at much greater currents (from 50 mA). A current of 100 mA is lethal to humans.

What does the RCD consist of?

The protective shutdown device includes a current transformer, an actuator (relay and a system of breaking levers), a self-test circuit. More advanced devices contain in their design a system of electromagnetic and inverse of the magnitude of the current cutoff (protection against short circuit currents and overload).

Principle of operation of the RCD

What it is? How does this device operate? Now let's talk about all this in detail. The principle of operation of the current transformer (TT) is based on the operation of the RCD. Phase and working neutral conductors pass through a current transformer. With normally operating equipment (with intact insulation), the values of the currents flowing through them are equal in magnitude but reverse in direction. As a result, they induce magnetic fluxes in the CT winding, which are equal in magnitude but reverse in direction, which completely compensate each other (there is no voltage at the ends of the secondary CT winding). If the insulation of equipment is disturbed, some of the current of the phase conductor flows to the ground through the ground conductor (if the housing of the device is grounded) or through a person who touched this electrical appliance. As a result of this, the value of the current flowing through the zero working conductor becomes less than the one going along the phase conductor. This leads to the fact that the magnetic fluxes in the transformer winding become different in magnitude. As a result, voltage appears at the ends of the CT winding. Through the relay connected to them, the current begins to flow. When the difference in the values of 30 mA is reached, the relay activates the system of breaking levers. The equipment is switched off.

Switching on RCD

It is made only after detecting and eliminating the malfunction of the electrical equipment that caused the device to operate, by pressing the cocking levers.

Conclusion

In this article, we introduced you in some detail to the RCD: what it is, how it works, and what it is used for. We hope that this information will be useful to you.